Sedimentological and Biological indicators of oceanic anoxic events (1d) inside upper Balambo Formation, L. Albian, northeastern Iraq

The study deals with succession from the upper part of the Late Albian Balambo Formation which are composed of fine-grained dark gray to black calcareous shale, limestone and marly limestone rich in sedimentary structures such as lamination, fissility and platy structures. Microfacies analysis revealed that mudstone, wackstone and few of يرامعملا دبع حلاف نورخآو 87 packstone are the main facies in the studied succession. The studied rocks generally are rich in organic matter and pyrite in addition to dominance of radiolaria, sponge spicules and foraminifera with elongated champers maybe “Schackoina” genus. All these characters indicate deposition in marine conditions with reduced or absent-oxygen condition that relate to oceanic anoxic event (1d).